Directional drilling with explosive charges



Dec. 25, 1962 L. H. ROBINSON, JR., ETAL.

DIRECTIONAL DRILLING WITH EXPLOSIVE CHARGES Y Filed July 11, 1960 3 Sheets-Sheet 1 FIG. 2.

FIG. I.

1 INVENTORS.

LEON H.ROB|NSON JR, ROBERT H. FRIEDMAN,

ATTORNEY.

H. ROBINSON, JR., srm. 3,070,011 DIRECTIONAL DRILLING WITH EXPLOSIVE CHARGES Dec. 25, 1962 3 Sheets-Sheet 2 Filed July 11, 1960 DE TON ATOR PLATE FIGLG- INVENTOR S.

LEON H-ROBINSON JR., ROBERT H.FRIEDMAN.,

3,070,01 I DIRECTIONAL DRILLING WITH EXPLOSIVE. CHARGES Filed July 11, 196 0 Dec. 25, 1962 L... H. ROBINSON, JR, ETAL 3 Sheets-Sheet 3 n w 9 V351: 7 Z:I 1 I m r vi r 1/ 9 n m m E:/ Ez}? w l A w M 7 v. 6 2 m 3 M .D L v 1 F A 7 v 4 J .a m .M M A m J@ /1. f WW I y W 8 o m w 2 I.

FIG.7. FIG.8. FIG.9 FIGJO FJ'GLII.

INV EN TORS LEON H ROBINSON JR.,( ROBERT H. FRIEDMAN,

rates ate Free 3,070,011 DRECTIONAL DRILLING WITH EXPLOSIVE CHARGES Leon H. Robinson, J12, and Robert H. Friedman, Houston,

Tex., assignors, by mesne assignments, to Jersey Production Research Company, Tulsa, 01:121., a corporation of Delaware Filed July 11., 1960, Ser. No. 42,089 7 Claims. (Cl. 10221.6)

This invention relates to directional drilling of boreholes, and more particularly to deviating boreholes, or drilling boreholes in given directions at an angle from the vertical, utilizing a succession of explosive charges including shaped-jet charges.

In connection with the drilling of boreholes in the earth for the purpose of exploiting possible hydrocarbon deposits therein, often it is desirable to drill boreholes at an angle from the vertical and in given directions. This technique may be necessary in order to by-pass sections of drill pipe that have become stuck in the bottom of the borehole, or to more economically penetrate given earth formations as when the earth formations are covered by a body of water.

.When directional drilling is necessary; it has been the practice to set a whipstock in a borehole and to utilize the wliipstock either to deflect a drill stern in a given di rection or to aim a shaped charge in a givendirection and at an angle from the vertical. It is manifest that setting whipstock to deflect drilling direction is an expensive procedure that should be avoided if possible.

In U.S. patent application Serial No. 855,681 for Apparatus for Drilling Boreholes with Explosive Charges, filed on November 27, 1959, now U.S. Patent No. 3,014- 423, by Leon H. Robinson, I12, and Robert H. Friedman, there is described a drilling technique utilizing a succession of explosive charges including shaped-jet charges; The explosive charges are pumped down a drill stem to the bottom of a borehole, are seated by suitable landing apparatus at or near the bottom of the drill stem, and are detonated to deepen and enlarge the borehole. The drilling technique described in this patent application will be found to be very flexible and to almost eliminate the necessity of round trips for the purpose of replacing drilling apparatus at the bottom end of the drill stem. The present invention may be advantageously used in connection with the technique described in patent application Serial No. 855,681, now U.S. Patent No. 3,014,423, in order to avoid the necessity of a round trip when it is desired to deflect the borehole from the vertical.

In accordance with the teachings of the present invention, a directional, explosive jet-shaped charge is utilized wherein having an elongated, preferably substantially cylindrical housing, encloses a directional explose jet-shaped charge wherein the conical liner is tilted away from the longitudinal axis of the housing so that, when it is detonated, it will direct an explosive jet in a direction offset from the longitudinal axis of the housing. Manifestly, it is necessary to provide means for orienting the direction of the explosive jet. In accordance with the teachings of the invention, this may be done by including in the firing circuit of the shaped charge a pair of spaced-apart electrical contacts which must be closed in order to detonate the shaped charge. The spaced-apart contacts are bridged by an electrical conductor mounted on a pivoted carrier member to which is aflixed a bar magnet. The carrier member is held against rotation and is released by apparatus responsive to the exertion of a predetermined diflerential pressure across the housing. When the differential pressure is exerted, the carrier is free to rotate and will so rotate in accordance with the force exerted on the bar magnet by the earths magnetic field. When the bar magnet has aligned itself, the drill pipe and shaped charge housing are rotated until the electrical contacts are bridged by the electrical conductor. At this point the jet-shaped charge will be detonated. In order to change the direction of detonation of the shaped charge it is only necessary to change the position of the electrical conductor with respect to the north pole of the magnet.

The objects and features of the invention will be more completely appreciated upon consideration of the following detailed description thereof taken in connection with the accompanying drawings wherein:

FIG. 1 is a schematic representation of a drilling rig including apparatus suitable for use in accordance with the explosive drilling technique;

FIG. 2 is a schematic representation of the bottom of i I the borehole containing a drill stern wherein the explosive drilling technique is being practiced;

FIG. 3 is an elevational view, partially in cross-section,

of explosive charge drilling apparatus in accordance with the present invention;

FIG. 4 is an illustration, partially in cross-section and 7 partially in schematic form, of the firing mechanism detonated in FIG. 3;

1 FIG. 5 is a sectional view of a fragmentary portion of the apparatus of FIG. 4 taken along the line 55 of FIG. 4;

FIG. 6 is a sectional view taken along section 66 of FIG. 4; and

FIGS. 7, 8, 9, 10, and 11 are schematic representations of the bottom portion of a borehole in the earth illustrating the various steps of directional drilling in accordance with the teachings of the present invention.

In FIG. 1 there is shown surface equipment for use in connection with the present invention. The usual drilling rig 1 is provided with an explosive charge loaders I platform 3 at a distance above the drilling floor 20 detercharge magazine housing 17. The function of the c arge injector housing is to accommodate a number of explosive charges so that individual explosive charges need not be manually inserted by the loader as the drilling progresses. However, this latter technique may be employed if it is so desired.

Connected to the swivel 19 is a Kelly joint 18 which extends through the rotary table 21 into the surface casing 25. Drilling fluid is circulated through the magazine housing 17 into the swivel 19 and Kelly joint 18 from the usual stand pipe 15 and hose connection 13. A mud pump (not shown) supplies pressurized drilling fluid to the stand pipe 15. Below the drilling floor 20 is located the usual mud return line 27 and blowout preventer 23. The mud return line 27 may be controlled by a valve 29. The mud control line is hydraulically coupled to the annular space between the surface casing 25 and the drill pipe in the usual manner.

As is shown most perspicuously in FIG. 2, the drill or well pipe 28 is provided with a landing nipple of landing seat 31 at or near its lower end. The purpose of the landingseat 31 is to receive a collar 45 or seating ring fitted around an exposive charge housing 33 which is pumped down the well through the drill pipe 28. When the collar 45 lands on the seat 31, flow of drilling fluid down through the drill pipe and out of the lower end thereof will either be stopped or substantally reduced so that a diiferential pressure will be built up across the explosive charge. As will be described below, differential 8 pressure is used for the purpose of firing the explosive charge.

At this point, it is advantageous to briefly describe the explosive drilling technique set forth in detail. in they aforementioned patent application Serial No. 855,681, now U.S. PatentNo. 3,014,423. This technique makes use of directional explosive jet-shaped charges alongwith nondirectional, gauging exposive charges. The function of thegauging explosivechargesis ,toenlarge the borehole to predetermined gauge afterone or more jet charges have, been detonated to deepen the borehole. The reason that the gauging charges are necessary isthat the. hole made by the shaped charges is elongated and tapered- After a shaped-jet charge has been detonated, the .drill,

pipe can be lowered only a short distance. The shapedjet charges and the gauging charges are injected into. the stream of drilling fluid going down the well pipe.

according to a predetermined sequence. First, a shaped charge is pumped down the well pipe after it seats.

on the landing seat 31, the explosive portionv of the jet charge isspaced a pr determine distance fromthe bottom of theborehole. A diiferenti-al pressure of predeter mined magnitude is built up acrossthe shaped charge.

then landedon' the seat 31 so as ,to. extend intothe holeproduced by the preceding shaped-jet charge or charges.

Preferably, the gauging charge is. long enoughto penetrate substantially the entire length of the hole blasted:

by the shaped-jet charge; The gauging charge, which This may be done one or more times 5 may be of a brisant' or unbrisant explosive materialor a combinationv thereof, is detonated while. tamped with r drilling fluid and preferably While under a hydrostatic pressure of at least 1000 psi. Drilling fluid is circulated after, ,each-detonationof an explosive charge so as to remove earth fragments and fragments of theexplosive charge housing from the bottom of theborehole. Prefer.-.

ably, the explosive charges ,are injected .into. the drill;

ing stream so as, to be spacedv apart substantially 100 to 4000 feet, and the drilling fluid is circulated so the particles therein are traveling at the rate of between.

100 and 400 feet per minute so that the successive explosive charges are detonated between 1 and 10 minutes.

apart.

With reference now to FIG. -3,v thereis shown a di-.

rectional exposive jet-shaped charge adapted to .defiect a borehole in a predetermined direction, In accordance withthe teachings of the present invention, the directional charge-includes an elongated housing havinga generally pointed, conical head 51. elongated body, portion. of the shaped chargewhousing is a seating ring 45, the function-of which is to ,seat on.

the landing seat or nipple 31 so'as to prevent the housing from being circulated out the bottom of the drill pipe, and to permit building up ofdifferential hydrostatic Fitted about the pressure across the housing. A flange 46 is provided at or near the upper end of the housing to prevent the seatingring 45 from slipping off of the housing.

plosive charge material. 43,'which is preferably brisant, is packed into the middle portion: of the housing; A.

conical liner 47 is provided for the purpose of shaping the exposive jet produced by the explosive charge material 43 in the usual manner. The axis 48- of the conical liner 47 does not coincide with the longitudinal axis 44 of vthe elongated housing In other words, the conical liner'is tilted, so that the explosive jet will be directed at an angle from the. longitudinal .axis of the housing.

The explosive charge material 43.-,is,packed between. the baffle or partition 38 and the conical linerv 47.

As mentioned above, theexposive charge. material is detonated by the exertion of differential pressure across;

the housing. Preferably, an electrically actuated deton-. atQr; 1- is. used. .tofietonatelhe; shaped. charge materiaL.

A mechanical firing mechanism, which will be described in detail with reference to FIGS. 4, 5, and 6, electrically energizes the detonator 41 responsive to differential pressure hydrostatically communicated through upper pressure tube 35 and lower pressure tube 37. Upper pressure tube 35 is in communication with the upper end of the explosive charge housing and lower pressure tube 37 extends from the firing mechanism 39 to the lower end of the housing'at the housing head 51.

With reference now to FIGS. 4, 5, and 6, there-is illustrated the details ofthe firing mechanism 39. The housing for the firing mechanism comprises two sections 53 and 55 which are bolted or otherwise connected together. The upper pressure tube 35 and the lower pressure tube 37 extend through the walls of the upper housing section 53. The interior of the upper housing section 53 is filled with .a suitable fluid such as water or glycerine. Flexible seals 59 and 65,. which may be of neoprene, are provided within the presseure tubes 35 and 37, respectively, so that hydrostatic pressure may.

be communicated to-the fluid 57 within-the upper housing'sections53 andyet physically isolate the interior of The reason for such the upper housing section 53. physicalisolation isv to prevent entry of dirt "and other extraneous mater'ial which :could impair the operation" of the apparatus to be described below. A- release collar 61 is in sliding fit over the end of lower pressure tube 37 that extends intothe upper housing section 53.

A spring 63 normally biases release collar 61 away' iromthe lower pressure tube 37 so that it engages the A flange 67 extends downwardl-yfrom the end of the release collar 61-for end of .upper .pressure tube 35.

purposes which will-become apparent below;-

Electrical energy for energizing detonator 41 is derived from 'a-mercury cell' 129. The electrical circuitwhich provides a surge current sufiicient toactivate the detona-- tor includes aresistor 123 and a capacitor-125 conr-iected to the; mercury cellby electrical lead 127, and a pair of spaced-apart electrical contacts 97 and 9S Contact'97 is connected to resistor 123 andcapacitor 125 by electrical The. circuit further includes electrodes and lead 121. 89 spaced apart on either side of a bore 84 through con tact housing or carrier 83, contacts 89 and 08 being con nected together, an electrical conductor 119 connecting the electrode 85 to detonator 41, and electrical conductor 131 connecting detonato'r 41 to mercury cell 129. The contact housing 83 is afiixed to lower housing section 55;

The. spaced-apart electrical contacts 97 and 98 are adapted to be bridged by. a'metal firing plate or conductor 104 which is mounted on a substantially cylindrical" 'magnet carrier member 113.

113 is pivotally supported by pivot bearings lfifi and 109- a flange 68a against which the head 63 of the pivot bearing member bears to hold the-pivot bearing 100 in place. The magnet carrier 113 houses a bar magnet and carries the metal firing plate 104. The metal firing plate 104 may be slid around the periphery of the magnet carrier 113 and may be set in various positions therearound by set-screws 104a.

The electrical contacts 97 and 98 and the electrodes 85 and 89 are supported in a contact housing which is con structed of. an electrically insulative material such as Plexiglas. The' contacts and electrodes are housed in recesses within the contact housing and are spring-biased outwardly therefrom, as shown. The electrodes 85 and 89' engage a dashpot. piston 91 which has a band 81 of electrically. conductive metal affixed thereto. The metal-.-

Magnet carrier member band 81 is positioned so as to connect together electrodes 85 and 89 when the dashpot is at the lower end of the dashpot cylinder 95. The space within which the apparatus is housed is filled with an incompressible liquid such as glycerin or distilled water. The dashpot piston is provided with a port 93 at the lower end thereof and a port 89 at the upper end thereof, which are hydraulically interconnected through the dashpot piston so as to permit slow passage of fluid therethrough. The dashpot piston is biased downwardly by coil spring 79 at the upper end thereof. The spring also engages the upper wall of the lower housing section 55. Extension 75a of the dashpot piston protrudes upwardly through the upper wall of the lower housing section 55 into the spaced defined by the upper housing section 53. A clevis '76 on release mechanism 71 hold the dashpot against the force of coil spring 79 in the position shown.

The release mechanism 71 is mounted on rollers so that it will slide readily to the right, as viewed. A flange 69 on the release mechanism 71 engages the flange 67 of the release collar 61. When the release collar is forced to the right, as viewed, it will drag the release mechanism along with it; when the clevis 76 no longer engages the head 75 the dashpot will begin moving downward. Likewise, when the flange 65a moves far enough to the right so that the head 68 of the pivot bearing 100 enters slot 72, the force exerted by spring 115 will be sufficient to move the magnet carrier 113 upwardly and to allow the magnet carrier to pivot freely when flange 99 engages the upper end of housing 55.

' The lowermost section of pipe 28 preferably is a section formed of a nonmagnetic material such as that made by Houston Oil Well Equipment Company for orientation of directional drilling deflecting tools and described on page 2402 of the Composite Catalog of Oil Field Equipment and Services, 195 859 edition.

The operation of the apparatus shown in FIGS. 3 through 6 will be described in conjunction with the stepwise illustrations of FIGS. 7 through 11. Let it be assumed that the borehole it has reached a depth at which it is desired to deflect the borehole off vertical and in a given direction, such as due east. The metal firing plate 104 will be moved to the position shown in FIG. 5. Assume that a shape charge, such as is shown in FIG. 3, has been pumped to the bottom of the pipe 28 so that seating ring 45 is landed on seat 31. In order to actuate the device, the pressure within pipe 28 is increased to at least a predetermined pressure. Flexible seal 59 will bulge inwardly under the force of the differential pressure between tube 35 and tube 37 and the incompressible fluid within upper housing section 53 will force the release collar 61 to the right. Release mechanism 71 will be dragged to the right by release collar flange 67. When the release mechanism 71 has moved a sufiicient distance, head 68 will no longer be held by the flange 68a and will move up into slot 72 under the impetus of spring 115. Simultaneously, clevis 76 will move to the right a suflicient distance to release head 75 so that the dashpot piston will move slowly downwardly under the impetus of spring 79. The magnet carrier 113 will move up relatively quickly as compared to the downward movement of dashpot piston 91. The magnet carrier may now pivot by virtue of the force exerted on the magnet 105 by the earths magnetic field. In view of the fact that the dashpot piston 91 moves quite slowly, the firing circuit of the detonator will not be completed should the metal firing plate 1M make the electrical connection between contacts 97 and 98 as the magnet carrier pivots. When the rotary movement of the magnet carrier ceases, the metal firing plate iii-d will be in the position shown in FIG. 5 relative to the contacts 97 and 98. When the dashpot piston 91 moves down to make contact between electrodes 85 and 89, the circuit will be in condition for firing when metal firing plate 1&4 makes electrical contact between contacts 97 and 8. The pipe 28 now may be rotated slowly. Contacts 97 and 98 will be moved around the periphery of the magnet carrier 113 until they both contact the metal firing plate 1'84. This will complete the electrical circuit to energize the detonator 41 and explode the shaped charge 43. A hole, such as is designated by the reference numeral 14!} in FIG. 7, will result. The drill pipe 28 may now be lowered a short distance (limited by the tapered shape of hole and a second charge similar to the one shown in FIG. 3 may be circulated to the bottom of the drill pipe and detonated in the same manner as described above. The resulting hole will be similar to that shown in FIG. 8 and designated by the reference numeral 144. As shown in FIG. 9, a gauging charge 146 may now be circulated down the drill pipe. The explosive charge may be contained in a semiflexible container so that it will penetrate to the bottom of the hole 144 and still permit the seating ring thereof to seat on the seat or nipple 31. The detonating charge will be detonated in the manner described in the aforementioned patent application Serial No. 855,681, now US. Patent No. 3,014,423. The resulting hole is designated in FIG. 10 by the reference numeral 148. The drill pipe may now be lowered as far as possible and a conventional straight shaped-jet explosive charge may be circulated to the bot tom of the drill pipe and detonated to form the hole designated by the reference numeral 152. After the drill pipe has been lowered again, if it is desired to still further deviate the borehole from the vertical, another explosive charge such as that shown in FIG. 3 may be circulated to the bottom of the drill pipe and detonated.

The invention is quite advantageous in that it is almost entirely automatic and virtually fool-proof. The shapedjet explosive charge cannot be detonated until the magnet carrier oscillation has settled down after the magnet carrier is released to pivot.

The invention is not to be restricted to the specific structural details, arrangement of parts, or circuit connections herein set forth, as various modifications thereof may be effected without departing from the spirit and scope of this invention.

What is claimed is:

1. Apparatus for explosive drilling at an angle from the vertical in a borehole traversed by a drill pipe having a seating means at the lower end thereof, comprising: an elongated, substantially cylindrical housing having a longitudinal axis; a seating ring operatively associated with said housing, adapted to seat on the drill pipe seating means so that differential hydraulic pressure may be exerted across said housing between a pair of spacedapart locations on the exterior of the housing; a shaped explosive jet charge within said housing for rotation therewith, comprising an explosive charge and a generally conical hollow in the explosive charge, the axis of said generally conical hollow being tilted at an angle to the longitudinal axis of said housing whereby said jet charge when detonated will direct a directional explosive jet at an angle to the longitudinal axis of said housing; and electrically actuable detonating charge operatively connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge; an electrical power source in said housing; a bar magnet; an electrically insulative carrier disk for said bar magnet, pivotally mounted in said housing and adapted to pivotally rotate with said bar magnet as said magnet aligns itself in accordance with the earths magnetic field; a contact carrier in said housing; a pair of spaced elec trical contacts on said contact carrier; means associated with said contact carrier for urging said electrical contacts against the periphery of said carrier disk; connecting means on said carrier disk for electrically connecting together said electrical contacts when said electrical contacts are at a given orientation relative to said magnet; and circuit means interconnecting said electrical power source, said electrical contacts, and said detonating charge to energize said detonating charge when said contacts are electrically connected by said connecting means. n p

2. Apparatus for explosive drilling at' an angle from the vertical in a borehole traversed by a drill pipe having a seating means at the lower end thereof, compris-' ing: an elongated, substantially cylindrical housing 'having a longitudinal axis; a seating ring operatively associated'with said housing, adapted to seat on the drill pipe seating means so that differential hydraulic pressure may be exerted across said housingbetwe'en a pair of spaced-apart locations on' the exterior of the housing; a shaped jet charge within said housing comprising an explosive and 'a conical liner extending upward into said explosive with its axis tilted at an angle with respect to the axis of said housing whereby the explosive jet produced by the explosive charge will be directed substantially along the axis of said conical liner; an electrically actuable detonating charge operativclv connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge;an electrical power source in said housing; a bar magnet; an electrically insulative carrier disk for said bar magnet, pivotally mounted in said housing and adapted to pivotally rotate with said bar magnet as said magnet-aligns itself 'in accordance with the earths magnetic field; a contact carrier in said housing; a pairof spa'c ed electrical contacts onsaid contact' carrier; means associated 'with said contact carrier for urging -said electrical contacts 'against the periphery of said carrier disk; connecting means on sai d carrier disk for electrically connecting together said electrical contacts when said electrical contacts are at a given orientation relative to said'magnet; circuit means inter-' connecting said electrical power source, said electrical contacts, and said detonating charge to energize said detonating charge when said contacts are electrically connected by said connecting means; a bore within said contact carrier; a 'dashpot mechanism comprising a dashpot cylinder connected to said housing and a electrically insu'lative dashpot piston positioned for reciprocating movement within said cylinder and saidbore; third and fourth electrical contacts within said, contact carrier, separated by said dashpot piston; conductive means on said'dashpot mechanism adapted to connect together said third 'andfourth electricalconta'cts when said dashpot piston is at one extreme of its range of movement; a coil spring on 'said'dashpot piston, engaging a portion of said housing for urging said dashpot piston toward said one extreme of its range of 'movement; restraining means in said housing connected to said dashpot piston andsaid'carrierdisk for holding said. 'dashpot piston awayv from saidlone extreme of its range of movement u to'the longitudinal axis of said housing whereby said jet charge when detonated will direct a directional explosive jet at an angle to the longitudinal axis of said housing; an electrically actuable detonating charge operrestraining means to r elease said carrier disk whereby said carrier diskjmay rotate to be oriented in accordance.

and for ho-lding'said carrier disk against pivotal rotation; 'and means connected to said restraining means and v hydraulically coupled to said longitudinally spaced-apart locations at the exterior of said housing, adapted 'to actuate said restraining meansto release said carrier disk an'd 'said dashpot piston whereby said carrier disk will be'oriented inaccordance with the force exerted by the earths magnetic field on said 'barmagnet, and said dashpot piston willslowly move toward said one extreme position thereofto connect together said third and fourth electrical contacts.

3. Apparatus for explosive drilling at an angle from the vertical in a borehole traversed by a drill pipe having a seating means at the lower, end thereof, comprising: an elongated, substantially cylindrical housing having a longitudinal-axis; a seating ring operatively associated with said housing, adapted to seat on the drill pipe seating means so that differential hydraulic pressure may be exerted across said housing between a pair of spacedapart locations on the exteriorof the housing; a shaped explosive jet charge within said housing for rotation therewith comprising an explosive charge and a generally conical hollow in the explosive charge, the axis of'said generally conical hollow being tilted at an angle atively connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge; an electrical power source in said housing; a bar magnet, an electrically insulative carrier disk for said bar magnet, pivotally mounted in said housing and adapted to pivotally rotate with said bar magnet as said magnet aligns itself in accordance with the earths magnetic field; a contact carrier in said housing; a pair of spaced electrical contacts on said contact carrier; means associated with said contact carrier for urging said electrical contacts against the periphery of said carrier disk, connecting means on said carrier disk for electrically connecting together saidelectrical contacts when said electrical contacts are at a given orientation relative to said magnet; restraining means connected to said carrier disk, for holding said carrier disk against rotation; means con nected to saidrestraining means and hydraulically coupled to said pair of longitudinally spaced apart locations at the exterior of said housing, adapted to actuate said means from connecting together said electrical contacts until said magnet is oriented by the earths magnetic field. 4' Apparatus for explosive drilling at an angle from the vertical in a borehole traversed by a drill pipe having a seating means at the lower end thereof, comprising: an elongated, substantially cylindrical housing having a longitudinal axis; a seating ring operatively associated with said housing, adapted to seat on the drill pipe seating means so that differential hydraulic pressure rnay be exerted across said housing between a pair of spaced-apart locations on the exterior of the housing; a shaped explosive jet charge within said housing forrotation therewith comprising an explosive charge and a generally conical hollow in the explosive charge, the axis of said generally conical-hollow being tilted at an angle to the longitudinal axis of said housing whereby said jet charge when detonated will direct a directional explosive jet at anangle to the longitudinal axis of'said housing; an electrically actuable detonating charge operatively connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge; an electrical power source in said housing; a bar magnet; an electrically insulative carrier disk for said bar magnet, pivotally mounted in said housing and adapted to pivotally rotate with said bar magnet as said magnet aligns itself in accordance with the earths magnetic field; a contact carrier in said housing; a pair of spaced electrical contacts on said contact carrier; means associated with said contact carrier for urging said electrical contacts against the periphery of said carrier disk; connecting means on said carrier disk for electrically connecting together said electrical contacts whensaid electrical contacts are at a given orientation relative to said magnet; restraining means connected to said carrier disk for holding said carrier disk the vertical in a borehole traversed by a drill pipe having a seating means at the lower end thereof, comprising: an elongated housing having a longitudinal axis; a seating ring operatively associated with said housing. adapted to seat on the drillpipe seating means so ha ifier nti l aomcu hydraulic pressure may be exerted across said housing between a pair of spaced-apart locations on the exterior of the housing; a shaped explosive jet charge within said housing for rotation therewith comprising an explosive charge and a generally conical hollow in the explosive charge, the axis of said generally conical hollow being tilted at an angle to the longitudinal axis of said housing whereby said jet charge when detonated will direct a directional explosive jet at an angle to the longitudinal axis of said housing; an electrically actuable detonating charge operatively connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge; an electrical power source in said housing; a bar magnet; an electrically insulative carrier disk for said bar magnet, pivotally mounted in said housing and adapted to pivotally rotate with said bar magnet as said magnet aligns itself in accordance with the earths magnetic field; a contact carrier in said housing; a pair of spaced electrical contacts on said contact carrier; means associated with said contact carrier for urging said electrical contacts against the periphery of said carrier disk; connecting means on said carrier disk for electrically connecting together said electrical contacts when said electrical contacts are at a given orientation relative to said magnet; circuit means interconnecting said electrical power source, said electrical contacts, and said detonating charge to energize said detonating charge when said contacts are electrically connected by said connecting means; and means in said housing connected to said shaped jet charge adapted to detonate said shaped jet charge responsive to exertion of a dillerential hydraulic pressure of predetermined magnitude between spaced-apart locations on said housing upon rotation of said shaped jet charge to a given orientation with respect to the earths magnetic field.

6. Apparatus for explosive drilling at an angle from the vertical in a borehole traversed by a drill pipe having a seating means at the lower end thereof, comprising: an elongated, substantially cylindrical housing having a longitudinal axis, a seating ring operatively associated with said housing, adapted to seat on the drill pipe seating means so that difierential hydraulic pressure may be exerted across said housing between a pair of spaced-apart locations on the exterior of the housing; a shaped explosive jet charge within said housing for rotation therewith comprising an explosive charge and a generally conical hollow in the explosive charge, the axis of said generally conical hollow being tilted at an angle to the longitudinal axis of said housing whereby said jet charge when detonated will direct a directional explosive jet at an angle to the longitudinal axis of said housing; an electrically actuable detonating charge operatively connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge; an electrical power source in said housing; first means in said housing including direction sensing means, electrically connected to said power source and to said detonating charge, adapted when activated to electrically energize said detonating charge upon rotation of said housing to a position whereat the axis of said conical hollow is pointed in a given direction; and means connected to said first means adapted to activate said first means when a predetermined differential hydraulic pressure is exerted between a pair of longitudinal, spaced-apart locations on the exterior of said housing.

7. Apparatus for explosive drilling at an angle from the vertical in a borehole traversed by a drill pipe having a seating means at the lower end thereof, comprising: an elongated, substantially cylindrical housing having a longitudinal axis; a seating ring operatively associated with said housing, adapted to seat on the drill pipe seating means so that differential hydraulic pressure may be exerted across said housing between a pair of spaced-apart locations on the exterior of the housing; a shaped explosive jet charge within said housing for rotation therewith comprising an explosive charge and a generally conical hollow in the explosive charge, the axis of said generally conical hollow being tilted at an angle to the longitudinal axis of said housing whereby said jet charge when detonated will direct a directional explosive jet at an angle to the longitudinal axis of said housing; an electrically actuable detonating charge operatively connected to said shaped charge adapted, when electrically energized, to detonate said shaped charge; an electrical power source in said housing; first means in said housing, in- "cluding a pivotally supported bar magnet, said first means being electrically connected to said power source and to said detonating charge being adapted to electrically energize said detonating charge when said housing is rotated so that said magnet assumes a given position in said housing; and means connected to said first means to hold said bar magnet against rotation within the housing until a predetermined hydraulic pressure has been exerted between a pair of longitudinally spaced apart locations on the exterior of the housing whereby said first means is deactivated.

References Qited in the file of this patent UNITED STATES PATENTS 

